The present invention relates to an automatic diaphragm control device for an objective lens provided with an automatic diaphragm in a closed circuit television (CCTV) camera. The objective lens diaphragm is controlled in response to brightness levels of video signals received by the television camera.
For the closed circuit television (CCTV) cameras in video systems, it has usually been necessary for the objective lens provided with an automatic diaphragm to contain a complicated control circuit comprising many elements and having functions not only of a light measuring mode conversion, but also of sensitivity regulation. Consequently, the objective lens has been too bulky to be easily handled. Further, there has recently been a tendency to provide lower source voltages for energization of such control systems as the development of a small-sized cameras has progressed, and there has developed a demand for a novel control circuit compatible with the lower power sources and small-sized cameras.